Detonators may be broadly divided into two types, either electric or non-electric, depending on the manner in which they are initiated. When detonators are attached to an initiation means such as electric leg-wires or signal tubing, the assembled unit is commonly termed a detonator assembly.
Electric detonators generally have a fuse head within the detonator shell, the fuse head being initiated by electric current transmitted along the leg-wires.
Non-electric detonators are commonly attached to a length of signal tubing, which comprises plastic tubing, lightly coated on the inside with a reactive powder which is capable of transmitting a shock wave to the detonator and thus initiating it.
The importance of safely protecting detonators during storage or transportation is clear. It is also important for sappers to be able to isolate detonators from causing injury to nearby persons.
Various attempts have been made in the past to protect detonators during storage or transportation.
For example, PCT published patent application WO9519539 describes a detonator protector, which is open at one end for insertion of a detonator and closed at the other end, and which radially encloses the base charge of the detonator. A wall is radially spaced around a detonator holder, so that a space is defined between the wall and the detonator holder. The free volume provided around the base charge of the detonator plus the outer are said to provide protection in the event that the detonator is accidentally detonated. The protector is constructed of high density polyethylene (HDPE).
Another example of a transportation holder and package for detonators is described in U.S. Pat. No. 5,133,258 to Rock et al. This is a non-propagating holder and package for explosive devices, such as blast caps. Each cap is contained in an internal cavity in a holder, and surrounded by radially-spaced, elastomeric walls. The holders are arrayed in a container, and absorb the energy released by accidental detonation of one cap to prevent sympathetic detonation of others in the package.